1. Field of the Invention
This invention relates to a jack incorporated into music apparatus, television sets, radio sets, etc. and more particularly to a compact internally split type jack whose casing is split into spaces for housing a plurality of contact pieces therein.
2. Prior Art
Commercial type jacks in general use, as shown in FIG. 4, are constructed of one chamber type casing 102 having a plug inlet 101 in front thereof and a required number of contact pieces 103, 104 and 105 placed inside the casing 102.
Jacks of the type described, however, have a common problem because a plug 106 inserted into the jack is chiefly held in position and alignment by a portion of a cylindrical plug inlet 101. The plug becomes loose with respect to the jack over time and with use, and the contact pieces are deformed by wrenching movements of the plug.
In an attempt to solve the problems described above, a jack as shown in FIGS. 5 and 6 has been proposed (Japanese Utility Model Publication No. 23266/1973). Particularly, the jack is of the construction in which a hole 114 for bringing the front end of the plug 113 inserted into the jack through a plug inlet 112 is formed in the rear wall 111 of a casing 110 having a required number of contact pieces 107, 108, 109 placed therein so as to prevent the plug 113 from becoming shaky by supporting the front end and base end portions of the plug 113 respectively in fixed relation with the plug inlet 112 and the hole 114.
In the jack of the type described above, however, because the front end portion of the plug more or less moves laterally and vertically before the end of the plug gets fitted into the hole 114 when the plug 113 is inserted into the plug through the inlet 112, there still remains the possibility that the contact pieces 107, 108 and 109 will become loose. Also, there is another disadvantage due to the great distance between the plug inlet 113 and the hole 114. It is not easy to fit the front end of the plug 113 into mating with the hole 114.
Furthermore, since the conventional jack of the above two types uses recoil spring type or slit-and-formed spring type contact pieces shown in FIGS. 4 to 6, the jack must have a casing considerably large enough in inner space to place a required number of such contact pieces inside the casing, with the result that the jack must be increased in size. This problem cannot be ignored in the light of the fact that music apparatus and the like have now the general tendency toward reduction in size.